Shelf



FIG. 1 is a front/right/top perspective view of a shelf showing my new design; a front/left/top perspective view would be a mirror image thereof;

FIG. 2 is a back/right/bottom perspective view thereof; a back/left/bottom perspective view would be a mirror image thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a left elevational view; a right elevational view would be a mirror image thereof;

FIG. 5 is a front elevational view;

FIG. 6 is a rear elevational view; and,

FIG. 7 is a bottom plan view thereof.

The broken lines depict portions that form no part of the claimed design. 

CLAIM The ornamental design for a shelf, as shown and described. 